The present invention relates generally to fine driving units, and more particularly to units for finely adjusting the positions and tilts of optical elements, such as lenses or mirrors, used in exposure apparatuses for fabrication of semiconductor devices or liquid crystal devices, etc. The present invention also relates to driving units for finely adjusting the positions and tilts of the optical elements to acquire accurate imaging in relation to the projection exposing images of the original forms (masks or reticles, etc.) onto objects (wafers, etc.) and to the exposure apparatuses using the same. The driving unit according to this invention is not only applicable to exposure apparatuses which needs fine adjustment to the position and tilt of the optical element, but also applicable to an apparatus, such as a sample stage of an electron microscope, which needs fine adjustment in vacuum state to avoid dusts or specific outgas.
A semiconductor exposure apparatus transfers different kinds of patterns on an original form (reticle) onto a silicon wafer (substrate). Besides improving resolution, it is also necessary to obtain overlay accuracy for fabricating a high integrated circuit.
The propagation of vibrations from inside and/or outside the exposure apparatus to an optical element (mirrors and the like) in the exposure apparatus lowers the resolution and/or overlay accuracy. For example, vibrations from outside the exposure apparatus can be the vibration of the building where the exposure apparatus is installed. There are two kinds of vibration from inside the exposure apparatus. One is caused and propagated to the optical element via a structure frame by operation of a reticle stage. The other is caused and propagated to the optical element by operation of an actuator for adjusting the optical element. The actuator for adjusting the optical element (a target) should be operated in two patterns to improve optical performance. The first pattern should be relatively static, with the actuator operated between the former exposure process and the latter exposure process. The second pattern should operate the actuator during exposing. The second one may have problems with vibration caused and propagated to the optical element by the actuator. The vibration which is generated by operation of the actuator to move the target, such as a mirror, causes a bigger problem, especially for EUV light (10 to 15 nm) used in an EUV exposure apparatus which has a shorter wavelength than KrF (248 nm) and ArF (193 nm) used in a conventional exposure apparatus. To improve the resolution and the overlay accuracy, a vibration controller for controlling the vibration by transforming vibration energy to other energies, such as heat energy, electrical energy, or mechanical energy, has been developed
Japanese Patent Application Publication No.11-233039 (JP11-233039) discloses a vibration controller using friction that can be used in vacuum state.
Japanese Patent Application Publication No.11-044834 (JP11-044834) discloses an actuator, which has vibration controlling function using the squeeze-film effect of a viscous material 34, such as oil or grease. FIG. 12 shows sectional perspective view of the actuator with vibration controlling functions using the viscous material 34 disclosed in JP11-044834. The actuator controls the output of a flange 32 by adjusting the pressure in a bellows 31 with a pressure controller (not shown). The actuator also controls the vibration by having the viscous material 34 in a gap formed in a support member and arranged in the bellows 31. This can provide a clean unit, for example, for maintaining outgas emitted from the viscous material 34 inside the bellows 31. The actuator, depending on the inserting method of the viscous material 34, in addition to eliminating the influence of unwanted outgas, can be used in vacuum state.
However, the method used in the vibration controller disclosed in JP11-233039 cannot be applied to an apparatus such as an EUV exposure apparatus which because the minute dust generated with the friction lowers the performance of the EUV exposure apparatus, is easily troubled by a little dust.
The method described in JP11-044834 may cause aged deterioration in the vibration control effectiveness due to the influence of the frequent vibration.